1. Field of the Invention
The present invention is related to a spread spectrum device and related random clock generator for a switching amplifier, and more particularly, to a spread spectrum device and related random clock generator capable of lowering electromagnetic interference of output signals of the switching amplifier.
2. Description of the Prior Art
Because a switching amplifier has a high operational efficiency approaching ninety percent, the switching amplifier becomes a primary choice of mobile devices with low power cost. Compared to traditional AB type of amplifiers at the same output wattage, the switching amplifiers have lower power cost and temperature because of higher operational efficiency. Despite the cost and space of radiators, the switching amplifiers in thin products are more and more popular. But output signals of the switching amplifiers are high frequency pulse signals so as to transpire electromagnetic interference through longer transmission lines easily. General solutions include adding a group of low-pass filters in the output end to filter out high frequency parts and outputting audio signals through transmission lines. But advantages of switching amplifiers are dramatically discounted because of the increased cost and space of low pass filters. Therefore, many techniques of decreasing electromagnetic interference are generated.
The popular prior art utilizes spread spectrum to randomly vary the operational frequency in a specific range for avoiding surpassing the requirements of electromagnetic compatibility because of switching frequency and centralization of harmonics energy. But linearity of the triangular wave generated in the prior art is not good and easily causes serious distortion problems.